1. Field of the Invention
This invention relates to a new and useful process for recovering oil from oil shale containing kerogen, a solid organic, primarily hydrocarbon, material having a high molecular weight, i.e., greater than about 3,000 grams/mole, which comprises about 10 to about 30 percent by weight of oil shale. The percentage recovery, as oil, of the organic matter originally present in the oil shale is low by most methods known in the art. Even the best operations result in relative high conversion of kerogen to carbon and permanent gases, which are of low economic value compared to liquid fuels. Consequently, a need exists for a simple process for recovering oil from oil shale which results in high yields of liquid product. Accordingly, the present invention provides a higher yield of liquid product by a process for recovering oil from oil shale containing kerogen which comprises contacting said oil shale at a reaction temperature of at least about 300.degree. C. with steam having a partial pressure of at least about 450 psia (3.1 MPa) and an organic solvent having a boiling point at ambient pressure, that is, about 15 psia (0.1 MPa), of at least about 80.degree. C.
2. Description of the Prior Art
U.S. Pat. No. 3,051,644 to L. D. Friedman teaches the recovery of oil from oil shale utilizing high pressure and high temperature steam. There is no mention of the use of a solvent and the pressure used is greater than that required herein (column 1, lines 12 to 17).
U.S. Pat. No. 2,601,257 to F. E. Buchan recovers oil from oil shale using a heavy hydrocarbon oil in the absence of steam and at lower pressures than required herein (column 5, lines 61 and 62).
U.S. Pat. No. 3,567,622 to O. R. Waltrip teaches the co-use of steam and hydrocarbon vapor at atmospheric pressure.
Furthermore, the kerogen conversions or the oil yields obtained in the prior art differ substantially from the results obtained by using the present invention herein. The kerogen conversions in the prior art are low. Specifically, the kerogen conversions for Buchan, Friedman, and Waltrip teachings are 61%, 65% and 55% respectively, in all cases less than 80%. However, in one embodiment of the present invention the yield is nearly 90%.